• Never be bold! Always "predict" something you know will happen!
• Be a little negative 'bout it! Say stuff like "I like the comapny, but I just don't see the game/hardware selling as much as you think." and "I hope I'm wrong." That way, you still win if you don't win the bet!
• Get a fanboy/hater! I'm going to name any, but these people always either overpredict, or underpredict! That way you win most of the time!
• Make sure the punishment for the loser isn't that bad, and the winner gets all the benefit! That way, in the case that you do loose, then you don't loose anything. And if you win, you win everything!
• Don't flame! This one speaks for itself.
• Learn to detect when someone else is using these techniques! It should be pretty obvious. 

Looks like I made betting irrelevant!

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Other tips:

Jizz_Beard_thePirate: Don't bet to begin with.

Or just never bet to begin with

/thread

I usually underpredict so......~.~
what am i.?

You say "how to never lose a bet", but your second point gives a strategy for saving face "even if don't win the bet"! False advertising :0

That is only for the people that don't heed the words and use this knowledge wiseley. If you use these carelessly, then there's a chance you won't win!

Just say that you would be happy if you were wrong, so no one can make fun of you if you don't win!

So I follow all this, amd still lose... what's next?

Use Jizz's advice!

Maybe for non nintendo stuff, but you just barely predicted 21 million combined sales for smash bros, thats quite a bit on the high end of predictions i have seen...